Chapter III: Face Preference Decision-Making And Visual Behavior
3.2 Gaze Cascade Study in Autism
3.2.2 Introduction
3.2 Gaze Cascade Study in Autism
and learning from a young age, resulting in decreased attending to social stimuli, which further disrupts normal development of cognitive processes related to social perception (Mundy
& Neal, 2000).
A large number of studies examining these social impairments have found a reduced attentional bias towards faces in ASD. When viewing complex social scenes, people with autism make fewer initial fixations to the person and to the face within a scene relative to controls, indicating thatthere is reduced spontaneous attentional capture by social stimuli (Fletcher-Watson et al., 2009). Similarly, in a selective attention task for which controls are unable to ignore irrelevant faces, people with ASD were found to be un-distracted, leading the authors to suggest that a deficit in the automatic processing of faces may underlie the diminished attentional bias for faces (Remington et al., 2012).
In addition to the reduced saliency of faces for people with autism, many studies have found that when people with ASD do fixate on faces, the pattern of visual behavior with respect to facial features differs from neurotypical viewing behavior. The exact nature of these differences, however, is far from clear. Some studies report reduced gaze to the eyes and increased reliance on information in the mouth region (Klin et al., 2002; Spezio, Adolphs, Hurley, & Piven, 2007), while other studies that similarly report reduced gaze to the eyes find little difference in gaze to the mouth region (Corden et al., 2008; Dalton et al., 2005).
Pelphrey and colleagues even reported reduced fixation time to all socially-salient regions of the face, including the eyes, nose, and mouth, and increased gaze to non-feature regions of the face (Pelphrey et al., 2002). The variable results have been attributed to a number of factors, including experimental differences in stimulus type (e.g., static/dynamic, computer- generated/real faces) and task demand (e.g., emotion judgment, gaze direction, etc.). However, a growing number of studies also propose that discrepant results arise, in part, due to the use of compensatory mechanisms or atypical processing strategies during certain types of face perception tasks, particularly by individuals who are high-functioning (Harms et al., 2010;
Joseph & Tanaka, 2003; Rice, Moriuchi, Jones, & Klin, 2012; Rutherford & McIntosh, 2006).
Abnormal gaze behavior in ASD is often accompanied by difficulties evaluating social information conveyed by faces, such as recognizing emotional expressions. Again, the findings are inconsistent, but some behavioral studies have found impaired recognition of basic emotions in ASD: compared to their neurotypical counterparts, people with autism are slower and less accurate in identifying certain negative emotional expressions such as anger, fear, and sadness (Ashwin et al., 2006; Bal et al., 2009; S. Wallace et al., 2008), though basic emotion recognition might still be preserved in high-functioning individuals (Castelli, 2005). There is stronger evidence, however, in support of impairments recognizing complex emotions, such as jealousy and trustworthiness, and making higher-level social judgments from faces that involve attributions of mental state (Adolphs et al., 2001; Baron-Cohen et al., 1997). Moreover, deficits in the ability to recognize facial expressions of emotions such as fear (Pelphrey et al., 2002) and sadness by people with ASD (Corden et al., 2008) are correlated with abnormal gaze to central features of the face, and particularly the eyes.
Two highly relevant aspects of social processing have, however, not been much investigated:
our preference decisions among social stimuli, and the temporal evolution of preference-based choices. First, most of the research on face processing to date focuses on emotion recognition or face perception in general, and few studies have investigated how these factors can influence our preferences of faces. Thus far, much of the research examining visual behavior in ASD has focused on atypical visual behavior and the nature of these impairments specifically in the context of objective decision-making, such as correctly identifying emotional expressions.
What is unknown, however, is whether these reported deficits also extend to making more subjective decisions, such as those involving face preference or attractiveness, which are just as relevant to social functioning, perhaps even more so. Secondly, it remains unknown how abnormal social judgments about faces might arise—what is the timecourse and possible underlying mechanism as atypical choices unfold?
Previous studies in typically developed individuals have investigated the cognitive processes involved in making preference choices. One class of models is known as drift diffusion models (DDM) and was initially proposed by Ratcliff and colleagues to describe two-choice decision processes (Ratcliff, 1978; Ratcliff & McKoon, 2008). These models assume that evidence for
each alternative is accumulated and integrated over time until a decision threshold is reached.
More recent studies have shown that integrating eyetracking data as an additional parameter in the DDM results in a model that better predicts choice and possibly reaction times (Krajbich, Armel, & Rangel, 2010).
Similar in form to the drift diffusion models is the gaze cascade phenomenon proposed by Shimojo and colleagues (S. Shimojo, Simion, Shimojo, & Scheier, 2003), emphasizing the behavioral dynamics of preference choice. In their model, it is proposed that preference and gaze mutually interact in a positive feedback loop to produce an effect known as a “gaze cascade.” Given a choice between two stimuli, individuals are initially just as likely to inspect one image in the pair as the other. However, in the few seconds before a preference decision is made, an increasing gaze bias occurs toward the eventually-chosen stimulus. Shimojo and colleagues propose that in the moments before this decision is made, a positive feedback pathway is engaged in which the gaze bias towards the to-be-chosen image leads to increased preference, which in turn increases gaze bias further, and so on, until the preference signal surpasses threshold leading to a behavioral decision. Thus in this model, gaze orienting is intrinsically linked to and necessary for decision-making and vice versa. Indeed, further evidence supporting the reciprocal effect of gaze on preference formation is demonstrated in experiment 2 of the same paper and a follow-up study using fMRI (Ito et al., 2014). In both studies, one face in a pair is presented on screen for a longer duration than the other face. After several repetitions, participants report a preference bias for the longer-presented face, indicating that manipulation of gaze can directly influence preference decisions. While the gaze cascade effect has been observed in other studies examining preference choice (Noguchi & Stewart, 2014; C. Simion & Shimojo, 2006), the effect may also extend to other types of visual decision-making tasks (Fiedler, 2012; Glaholt & Reingold, 2009; Wiener, Hölscher, Büchner,
& Konieczny, 2011).
Given that the literature suggests atypical viewing behavior in ASD is accompanied by deficits in processing social information, the current study sought to examine the influence of gaze on preference choice in autism and, specifically, whether eye movements reveal a fundamentally different evaluation process in ASD. Eye-tracking was used to investigate gaze behavior in
adults with high-functioning autism while they made preference decisions amongst pairs of social and non-social stimuli. Since direct gaze can elicit atypical visual behavior in ASD, we utilized face stimuli depicting open eyes as well as closed eyes so that we could determine whether a potentially abnormal “gaze cascade” effect was caused by an avoidance of direct gaze, or rather by an overall difficulty in making self-paced preference judgments for faces.
Furthermore, we tested whether the typically robust gaze cascade would remain intact under time pressure by using a time restriction in one block. Consistent with evidence that individuals with ASD have difficulty evaluating and making social judgments about faces, and given evidence of reduced attention to faces and direct gaze in ASD, we predicted that the ASD group would not have a normal gaze cascade, take longer than controls to make preference choices regarding faces, and end up making unusual preference choices. To our surprise, we found an essentially typical gaze cascade, normal final preferences, and faster decision times in ASD.
3.2.3 Materials and methods